Utilizing normal rat and mouse prostates as well as the Dunning prostatic adenocarcinoma, prostatic involution will be studied to achieve a fuller understanding of the process of prostatic regression at the morphological, cellular, and molecular levels. New findings from this research should provide the insights necessary to design new therapies for treatment of prostatic adenocarcinomas. The involutional process will be analyzed at the light and electron microscopic levels to assess differential cellular effects of androgen deprivation in proximal versus distal ductal regions of normal rat and mouse prostates. Changes in the prostatic stromal population (fibroblasts and smooth muscle cells) following castration will be examined histologically and immunocytochemically to assess cellular loss and/or dedifferentiation of these cells following castration. Changes in the extracellular matrix and basement membranes will also be assessed by autoradiography and immunocytochemistry to assess the status of basement membrane proteins, their synthesis and degradation. Loss of functional (secretory) activities will be examined by immunocytochemistry to determine the temporal and spatial aspects of loss of epithelial secretory function in proximal versus distal prostatic ducts. Analysis of chimeric prostates composed of wild-type stroma+Tfm (testicular feminization) epithelial cells will be performed to determine the role of epithelial androgen receptors in prostatic regression. Utilizing 3H-thymidine autoradiography prostatic epithelial cell lineage will be examined to determine whether the selection of cells for programmed cell death following androgen deprivation is based upon the proliferation history of the epithelial cells, whether spatial factors (proximal versus distal ducts) are involved, or whether the process is random. Finally, the molecular mechanism of prostatic regression will be studied by examining the expression of a testosterone repressed gene (TRPM-2) and its mode of action. For this purpose the expression of TRPM- 2 will be assessed via Northern analysis, in situ hybridization, and by immunocytochemistry. The cell biology of TRPM-2 action will be assessed by transfection of a dexamethasone-regulated TRPM-2 gene construct or by direct microinjection of the TRPM-2 protein into tissue culture cells to assess whether the action of this regression-associated protein affects cell shape, cytoskeleton, or nuclear events. All specific aims will be examined through use of both normal and neoplastic prostatic tissue.